linux-kernel - [PATCH v2 2/8] PCI: Add ACS quirk for Amazon Annapurna Labs root ports

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Message-ID: <20190718094531.21423-3-jonnyc@amazon.com>
Date:   Thu, 18 Jul 2019 12:45:25 +0300
From:   Jonathan Chocron <jonnyc@...zon.com>
To:     <lorenzo.pieralisi@....com>, <bhelgaas@...gle.com>,
        <jingoohan1@...il.com>, <gustavo.pimentel@...opsys.com>,
        <robh+dt@...nel.org>, <mark.rutland@....com>
CC:     <dwmw@...zon.co.uk>, <benh@...nel.crashing.org>,
        <alisaidi@...zon.com>, <ronenk@...zon.com>, <barakw@...zon.com>,
        <talel@...zon.com>, <hanochu@...zon.com>, <hhhawa@...zon.com>,
        <linux-pci@...r.kernel.org>, <linux-kernel@...r.kernel.org>,
        <devicetree@...r.kernel.org>, <jonnyc@...zon.com>
Subject: [PATCH v2 2/8] PCI: Add ACS quirk for Amazon Annapurna Labs root ports

From: Ali Saidi <alisaidi@...zon.com>

The Amazon's Annapurna Labs root ports don't advertise an ACS
capability, but they don't allow peer-to-peer transactions and do
validate bus numbers through the SMMU. Additionally, it's not possible
for one RP to pass traffic to another RP.

Signed-off-by: Ali Saidi <alisaidi@...zon.com>
Signed-off-by: Jonathan Chocron <jonnyc@...zon.com>
---
 drivers/pci/quirks.c | 19 +++++++++++++++++++
 1 file changed, 19 insertions(+)

diff --git a/drivers/pci/quirks.c b/drivers/pci/quirks.c
index 208aacf39329..23672680dba7 100644
--- a/drivers/pci/quirks.c
+++ b/drivers/pci/quirks.c
@@ -4366,6 +4366,23 @@ static int pci_quirk_qcom_rp_acs(struct pci_dev *dev, u16 acs_flags)
 	return ret;
 }
 
+static int pci_quirk_al_acs(struct pci_dev *dev, u16 acs_flags)
+{
+	/*
+	 * Amazon's Annapurna Labs root ports don't include an ACS capability,
+	 * but do include ACS-like functionality. The hardware doesn't support
+	 * peer-to-peer transactions via the root port and each has a unique
+	 * segment number.
+	 * Additionally, the root ports cannot send traffic to each other.
+	 */
+	acs_flags &= ~(PCI_ACS_RR | PCI_ACS_CR | PCI_ACS_SV | PCI_ACS_UF);
+
+	if (pci_pcie_type(dev) != PCI_EXP_TYPE_ROOT_PORT)
+		return -ENOTTY;
+
+	return acs_flags ? 0 : 1;
+}
+
 /*
  * Sunrise Point PCH root ports implement ACS, but unfortunately as shown in
  * the datasheet (Intel 100 Series Chipset Family PCH Datasheet, Vol. 2,
@@ -4559,6 +4576,8 @@ static const struct pci_dev_acs_enabled {
 	{ PCI_VENDOR_ID_AMPERE, 0xE00A, pci_quirk_xgene_acs },
 	{ PCI_VENDOR_ID_AMPERE, 0xE00B, pci_quirk_xgene_acs },
 	{ PCI_VENDOR_ID_AMPERE, 0xE00C, pci_quirk_xgene_acs },
+	/* Amazon Annapurna Labs */
+	{ PCI_VENDOR_ID_AMAZON_ANNAPURNA_LABS, 0x0031, pci_quirk_al_acs },
 	{ 0 }
 };
 
-- 
2.17.1